I am not a developer on the platform personally, so could not provide these. I moved your other ticket to our developer connection forum to see if someone can assist you.
It has not produced orphaned posts. It has left the posts as guest posts, as the members have been deleted. This has been the same functionality for multiple decades on the platform, and is used on many occasions by our users who do not wish to remove posts when they delete a user.
As I mentioned above, I understand it may not have been your intention, however this does not make the function incorrect.
I completely understand your frustration here, but unfortunately you are trying to do things quicker than anyone can possibly assist you in any way. You have had a post moved to the developer section to see if someone can assist. In the meantime you have gone ahead and done Something that has caused you unintended consequences. If I can offer one bit of advise, it would be to slow down a little. For example, you have typed 1 response, edited that response with more, and posted another reply, all while I am typing a single response to you.